Potentiometers



July 5, 1955 5 PANTAGES 2,712,584

POTENTIOMETERS Filed Aug. 5, 1954 3 SheetsShe'et l 1N VEN TOR. S72v5 Bv/vmaes ATTOR/VEX July 5, 1955 s, PANTAGES 2,712,584

POTENTIOMETERS Filed Aug. 5, 1954 3 Sheets-Sheet 2 I $5 I'll 1 -10- 1o to IN V EN TOR.

/z+ STEVE 7% 465.5 HQ' I BY%' l United States Patent 6 POTENTIOMETERS Steven Pantages, New York, N. Y. Application August 5, 1954, Serial No. 448,027

18 Claims. (Cl. 201-56) The present invention relates generally to potentiometers or variable resistances, and is a continuation-in-part of the matter contained in my application Multiple Remote Control Switch, Serial No. 333,693, filed January 28, 1953.

A primary object of the invention is to provide a potentiometer, variable resistance device and the like, wherein a movable contact support travels through a space defined between two parallel members with the latter both carrying portions of the resistance element, delay line or other similar electrical conducting element, so that contacts on the movablesupport can be successively engaged with the portions of the resistance element to permit the inclusion of an element of extreme length within a restricted space, or so that the contacts can simultaneously engage both portions of the resistance element to provide a desired relationship between the variation of the resistance included in a circuit and the movement of the contact support.

One aspect of the present invention resides in the provision of a potentiometer or variable resistance device including a body having parallel, spaced apart walls, which can be fiat or cylindrical, and carry respective portions of the resistance element, arranged either spirally, helically or otherwise, so as to define a continuous circuit, with contact means being movable through the space between said walls along a closed path and suitably guided to first move along one portion of the resistance element, then along the other portion of the resistance element and then back to the first portion of the resistance element thereby to permit continuous movement of said contact means along said closed path in either direction.

Another aspect of the invention provides a potentiometer or variable resistance device including a body having parallel, spaced apart, flat walls, a contact support movale along an orbital path between the walls which carry oppositely spiralled resistance elements, and two connected contacts on the support guided to follow the respective resistance elements and simultaneously contacting the latter to include complementary portions of the resistance elements in the resistance circuit, whereby the total resistance of the circuit varies linearly as the contact support is moved along its orbital path.

Another object is to provide a potentiometer or variable resistance device of the described character with an indicator cooperating with a suitably calibrated scale to show, at all times, the condition of the device.

A further object is to provide a potentiometer or variable resistance device of the described character which is constructed and arranged to provide a minimum of frictional resistance to the movement of the contactor along the extended resistance element thereby to facilitate operation of the device.

These and other objects, features and advantages of the invention will be apparent in the following detailed description of illustrative embodiments thereof, presented merely by way of example, when said description is read in connection with the accompanying drawings which form a part hereof, and wherein:

Fig. 1 is a front, elevational view of a potentiometer embodying the present invention;

Fig. 2 is a vertical, sectional view taken along the line 2-2 of Fig. 1;

Fi 3 is a sectional view taken along the line 3-3 of Fig. 2, with a resistance element which would not normally be visible in such a view being represented by broken lines;

Fig. 3a is a wiring diagram showing the connections of the contacts and resistance elements in the embodiment of the invention illustrated in Figs. 1, 2 and 3;

Fig. 4 is a fragmentary, sectional view taken along the line 44 of Fig. 3 to show means whereby engagement of the contacts can be shifted from one resistance element to the other;

Fig. 5 is a fragmentary, detail view, partly in section and on an enlarged scale, of a contact structure included in the device of Figs. 1 to 4, inclusive;

Fig. 6 is a fragmentary detail view, partly broken away and in section, of a preferred contact structure which can be substituted for that shown in Figs. 2 and 5;

Fig. 7 is a view similar to Fig. 3, but showing the arrangement of resistance elements in another embodiment of the invention;

Fig. 8 is a wiring diagram showing the connections of the contacts and resistance elements in still another embodiment of the invention;

Fig. 9 is a view similar to Fig. 2, but showing the structural arrangement of the embodiment represented in Fig. 8;

Fig. 10 is a detail sectional View taken along the line 10-10 of Fig. 9, but on an enlarged scale;

Fig. 11 is a sectional view taken along the line iii-11 of Fig. 12 and showing still another embodiment of the invention;

Fig. 12 is a sectional view taken along the line 12-12- of Fig. 11;

Fig. 13 is an axial sectional View of still another embodiment of the invention;

Fig. 14 is an enlarged detail of a contact arrangement forming part of the embodiment of Fig. 13;

Fig. 15 is a fragmentary front elevational view of the central portion of the front wall of the casing which is obscured in Fig. 1;

Fig. 16 is a fragmentary, enlarged sectional view taken along the line 1616 of Fig. 17;

Fig. 17 is a fragmentary, enlarged detail view of a portion of the structure appearing in Fig. 15;

Fig. 18 is a fragmentary, sectional view showing an arrangement for shifting the contact from one resistance element to another resistance element in still another embodiment of the invention, the section being taken along the resistance elements; and

Fig. 19 is a sectional view taken along the line 19-19 of Fig. 18.

Referring to the drawings in detail, and initially to Figs. 1, 2 and 3, thereof, a potentiometer or variable resistance device embodying this invention is there illustrated and generally indicated by the reference numeral 29. P0- tentiometer 20 includes a casing made up of front and rear walls 21 and 22, respectively, held in spaced apart, parallel relationship by an annular side wall 23. The casing is preferably formed of an electrical insulating material, which may advantageously be an easily molded or otherwise formed plastic resin.

An actuating shaft 24 is journalled in suitable hearings in the walls 21 and 22 and extends through the front wall 21 to receive an actuating knob 25. Between the walls 21 and 22, shaft 24 carries a radially extending contact support arm 26 which is mounted to permit radial movement of the latter during its angular or turning movement with shaft 2 For example, as shown in the drawings, shaft 24 is provided with a diametrically extending, open-ended tube 27, preferably of non-circular cross-sectiomwhich telescopically receives arm 26 having the same noncircular cross-section to prevent turning of the arm about its own longitudinal axis.

A contact member 28 is carried by arm 26 adjacent one end of the latter and is movable in the direction parallel to the axis of shaft 24 so as to be alternately engageable with one of the other of two resistance elements, de lay lines or similar electrical elements, 29 and 3t) respectively carried by the walls 22 and 21 of the casing. Each of the resistance elements 29 and 3% is in the form of a spiral having several turns, with the spiral of element 29 being in one direction and the spiral of the element 36, shown in broken lines on Fig. 3, being in the opposite direction. Further, as seen on Fig. 3, the outer and inner ends of the spiralled resistance elements 29 and 38 are radially aligned and circumferentially overlapped, with the outer ends of the resistance elements being electrically connected, as by a conductor 31 (Fig. 3a), and with the terminals 32 and 33 of the potentiometer being respectively connected to the contact member 28 and to the inner end of one of the resistance elements, for example, to the inner end of element 29 (Fig. 3a).

Thus, movement of contact member 28 along element 29, from the inner end to the outer end of the latter, will interpose a progressively increased resistance between the terminals 32 and 33. When contact member 28 reaches the outer end of resistance element 29, it is shifted into contact with the outer end of resistance element 33. Further, movement of contact member 28 along element 30 adds progressively increasing lengths or" that element to the complete resistance of element 29, and the maximum resistance is interposed between the terminals when the contact member reaches the inner end of element 39 whereby the entire length of the latter is in series with the entire length of resistance element 29. Upon reaching the inner end of element 3t), contact member 28 is again shifted to once again engage the inner end of element 2? whereby a minimum resistance is interposed between terminals 32 and 33.

It is to be understood that the movement of contact member 28 along spiral resistance element 2% and then along spiral resistance element 30 is effected by rotation of shaft 24 in one direction, for example, in the clockwise direction, as viewed on Fig. 3, with the contact member and its support arm 26 undergoing the necessary radial movements as the contact member follows the turns of increasing and then decreasing radii of the resistance ele ments. in the embodiment of the invention illustrated in Figs. 1, 2 and 3, the radial movement of the contact member is achieved by spiral grooves 3d and 35 in which the resistance elements 29 and 39 are respectively disposed. Thus, during the engagement of contact member 28 with resistance element 2?, the contact member rides in groove 34 and is guided by the latter, and similarly the groove 35 guides the contact member during engagement of the latter with the resistance element 39.

As previously noted, the potentiometer 29 automatically shifts the contact member 28 from a position engaging one of the elements 29 and 30 into engagement with the other of the resistance elements whenever the contact member reaches the end of the resistance element with which it has been in engagement. For this purpose, the adjacent ends of the grooves 34 and 35 are inclined, as at 36 (Fig. 4), and the contact member 28 has a length substantially equal to the distance L (Fig. 2) from the inner face of one of the front and rear walls 21 and 22 to the resistance element in the groove of the other of said walls. Thus, as the contact member 23 reaches an end of one of the grooves 34 and 35 and rides on the inclined portion 36 thereof, the contact member is axially shifted, as indicated in broken lines on Fig. 4, into engagement with the adjacent end portion of the resistance element in the other of the grooves. During travel along either of the resistance elements 29 and 3% the end of the contact member 28 remote from the end engaging the resistance element in the related groove rides against the inner face of the opposite wall 2i or 22 thereby to maintain contact between member 28 and the resistance element then engaged thereby.

Further, the contact member 23 is preferably yieldably held in each of its two axially shifted positions. For example, as shown in Fig. 5, the contact member 23 is formed with two spaced recesses 36 and 37 which are engageable by a detent ball 38 movable in a bore of arm 21; and urged by a spring 39 against the movable contact member 28 to engage in recess 36 for holding the contact member in a position to engage resistance element 29, or to engage in recess 37 for holding the contact member in a position to engage resistance element 36.

it will be apparent that the potentiometer 29 described above in connection with Figs. 1 to 5, inclusive, permits a great variation in the value of the resistance interposed between the terminals 32 and 33 by reason of the fact that resistance elements, each formed of several turns, are carried by both of the walls 21 and 22. Further, the arrangement of the resistance elements 29 and 30 with their ends adjacent to each other, both radially and circumferentially, and the automatic shifting of the contact member 28 from one resistance element to the other, permits the continuous rotation of the knob 25 and actuating shaft 24, in either the clockwise or counterclockwise directions, thereby to increase and decrease the resistance interposed between the terminals.

Further. in accordance with the present invention, a potentiometer, for example, the potentiometer 20 of Figs.

1, 2 and 3, is provided with means for indicating the value f the resistance interposed between the terminals 32 and 33 in all rotational positions of the knob 25 and shaft as. For this purpose, an indicating arm or pointer 40 extends siidably through a diametrical bore 41 (Fig. 2) in the hub of hollow knob 25, and the pointer 4t), at its end within the hollow knob is provided with a pin assembly 42 which engages in a suitable guide groove 43 formed in the outer face of front wall 21 within the confines of the hollow knob. Guide groove 43 is preferably of spiral configuration and a suitably calibrated resistance indi cating scale 44 extends spirally on the portion of the outer face of wall 21 disposed radially outward of the knob to cooperate with the pointer 40 in indicating the value of the resistance, voltage drop or delay provided by the potentiometer in any of the positions of the contact member thereof. It is apparent that the groove 43 will have as many turns as are included in the elements 29 and 30 together, so that the tip of pointer 40 registers both radially and circumferentially with the inner ends of groove 43 and scale 44, when contact member 23 engages the inner end of element 29, and the tip of the pointer registers with the outer ends of the indicating scale and the related guide groove when the contact member reaches the inner end of element 36 after travel along the full lengths of both resistance elements.

In order that the above described indicating means will not interfere with the continuous rotation of the knob 25, shaft 24 and contact support arm 26, a return groove 43a (Fig. '15) connects the inner and outer ends of groove 43. Groove 43a is substantially deeper than groove 43 (Fig. 16) and at its opposite ends has inclined portions merging with the adjacent ends of groove d3. Pin assembly 42 includes a housing 42a in which a-pin 42b is slidable and a guide shoe 420 at the end of pin. 421) to engage successively in the grooves 43 and 4311. A spring 42d is disposed in housing 42a and acts on the pin in the direction urging the shoe 42c toward the bottoms of the grooves 43 and 43a. As seen in Figs. l6 and 17, shoe 42c is of rectangular plan form and has a length longer'than the distance across either of the grooves and 43a so that, when shoe 420 is moving along one of said grooves, it will bridge the other of said grooves at the intersections, whereby the shoe is transferred from one groove to the other only at the connecting ends of the grooves. It is apparent that, with indicating means constructed as above, the knob can be continuously rotated in one direction.

While the contact member 28 shown in Figs. 2 and 5 is suitable for the purposes described above, it results in relatively great frictional resistance to the rotation of knob 25 by reason of the engagement of one end or the other of the contact member in the guide groove 34 or 35. In order to reduce the frictional resistance caused by engagement of the contact member in the guide grooves, the contact member is preferably provided with rollers adjacent its opposite ends to eifect rolling contact with the inner or outer side wall of the guide groove. For example, as shown in Fig. 6, the contact member 28a, which is axially movable in the outer end of arm 26a, has rollers 46 and 47 mounted rotatably thereon adjacent its outer ends with contacts 48 and 49 projecting beyond rollers 46 and 47 for engagement with the resistance elements 2% and a in the guide grooves 34a and a, respectively. It will be noted that the contacts 48 and 49 have smaller diameters than the rollers 46 and 47, while the latter are slightly smaller diametrically than the widths of the grooves 34a and 35a. Accordingly, the contacts 48 and 49 are spaced from engagement with the sides of the grooves 34a and 35a by the rollers 46 and 47, while the latter only engage the inner or outer side of the related groove to roll along the engaged side as the contact 48 or 49 moves along the related resistance element 29a or 30a.

Although the embodiment of the invention illustrated in Figs. 1, 2 and 3 included two resistance elements 29 and 30 of equal length arranged in oppositely directed spirals, so that each element includes several turns, it is to be understood that the invention is not limited to such an arrangement, and that the resistance elements on the two walls 21 and 22 may each have only a single, circularly arranged turn or, as shown in Fig. 7, one of the resistance elements and its guide groove, represented in broken lines at 34b, may have several spirally arranged turns, while the other resistance element 30b and its guide groove 35b merely forms a short return path for the contact member 2817 between the outer and inner ends of the resistance element and groove 34b.

Further, although in the embodiment of the invention illustrated in Figs. 1, 2 and 3 contact is effected with the resistance elements 29 and 30 in succession, the

invention may be incorporated in a potentiometer or variable resistance device having resistance elements arranged on two spaced apart walls and wherein such elements are simultaneously engaged by contact members to provide a resistance which varies as a predetermined function of the movement of the contact members.

For example, referring to Figs. 8, 9 and 10, a potentiometer generally indicated by the reference numeral 200 is there shown to include a casing of insulating material having front and rear walls 21c and 220 which respectively carry spirally arranged resistance elements 3% and 2% disposed in related spiral grooves 35c and S te. In the potentiometer illustrated in Figs. 1, 2 and 3, the variation of the resistance achieved by each complete revolution of the shaft 24 differs as the contact member 28 travels over the radially inner or outer turns of the resistance element with which the contact member is engaged. However, in the potentiometer 200 of Figs. 8, 9 and 10, the resistance elements 290 and 30c, arranged in oppositely directed spirals, are simultaneously engaged by the contact member, generally indicated by the reference numeral 28c (Fig. 8), so that during each revolution of the shaft 240 an equal length of the combined resistance element is either added to, or subtracted from, the total resistance, thereby to pro vide variation of the resistance as a linear function of the rotation of shaft 24c. As seen in Fig. 8, the terminals 32c and 33c of potentiometer 200 are respectively connected to the inner and outer ends of the resistance elements 2% and 3%. Further, the contact member 28c includes contacts and 51 which are radially slidable, independent of each other, along a support arm 26c which extends from the actuating shaft 24c, so that the contacts 50 and 51 can simultaneously engage the resistance elements 290 and 36c at complementary portions of the spirals thereof. Thus, the minimum resistance is achieved when contacts 50 and 51 engage the inner and outer end portions of the resistance elements 290 and 390, respectively. When shaft 24c is rotated, by manual actuation of the knob 25c, in the direction effecting movement of contact 50 along element 2% toward the outer end of the latter, contact member 51 simultaneously moves along resistance element 39c toward the inner end of the latter. During the first revolution of shaft 240, contact 50 traverses an inner turn of the resistance element 290 while contact 51 traverses an outer or relatively large turn of resistance element 300. As rotation of shaft 240 is continued, the turns traversed by contacts 54 increase in circumference, while the turns traversed by contact 51 are correspondingly decreased in circumference. Thus, the total length of resistance which is either added to, or subtracted from, the effective resistance during each revolution of shaft 240 will be substantially constant to provide variation of the resistance as a linear function of the rotation of shaft 240.

Referring to Figs. 9 and 10 of the drawings, it will be seen that the support arm 260 preferably is of H- shaped cross-sectional configuration to define two guide channels 52 and 53 opening, respectively, toward the inner surfaces of the walls 220 and 21c. Each of the contacts 50 and 51 preferably includes a base 54 slidable in the related channel 52 or 53, and a roller 55 adjacent the free end of the contact to cooperate with the groove 340 or 350, in the same manner as rollers 46 and 47 of the embodiment illustrated in Fig. 6, thereby to reduce the frictional resistance to movement of the guided contacts along the related resistance elements.

While all of the above described embodiments of the invention have had the resistance elements thereof disposed within the grooves which function to guide the contacts along the resistance elements, it is to be noted that the present invention is not limited to arrangements of that character, and that the guide grooves for the contact member or members may be remote from the resistance elements. For example, as shown in Figs. 11 and 12, the potentiometer 29d there illustrated has guide grooves 34d and 35d formed in the radially inner portions of the inner or confronting faces of rear wall 22d and front wall 21d, while the resistance elements 29d and 300. are disposed on the walls 22d and 21d, respectively, at locations radially outward with respect to the related guide grooves. A contact support arm 26a is slidable in a diametrically extending tube 27d carried by the rotatable shaft 24d, and the outer end of arm 26a' is formed as a guide channel member 56 extending parallel to the axis of shaft 24d and carrying the contact member, which is generally identified by reference numeral 28d.

Contact member 28d includes a portion 57 slidably disposed in the guide channel member 55 and having a guide member 58 joined thereto for selectively engaging in one or the other of the guide grooves 34d and 35d. An extension 59 extends radially outward from guide member 58 and carries a contact 66 which engages resistance element 29d, when guide member 58 is received in guide groove 34a, and which engages resistance element 39d, when guide member 58 is disposed in guide groove 35d. It is to be understood that guide member 58 cooperates with the grooves 34d and 35d and is shifted axially from engagement with one of said grooves into engagement with the other of said grooves, in the same cooperative manner as has been previously described in connection with the contact member 28 and the grooves 34 and 35 of the embodiment of the invention illustrated in Figs. 1, 2 and 3.

From the foregoing, it is apparent that guide member 58 cooperates with the grooves 34d and 35d to determine the paths which the contact 60 follows on the resistance elements 29d and 30d, successively. The resistance elements 29d and 30d may be each in the form of a spirally arranged resistance wire, as in the embodiment of Figs. 1, 2 and 3, or, as shown in Figs. 11 and 12, the resistance elements 2d and 30d may each be in the form of a relatively Wide annular strip of resistance material, for example, of carbon, with the position of engagement of the contact with the relatively wide strip, as determined by the guide grooves 34d and 35d, establishing the resistance or delay interposed in the circuit by the potentiometer. Further, while the grooves 34a and 35d of the embodiment illustrated in Figs. 11 and 12 are in the forms of spirals, it is to be understood that such grooves may have any desired configuration in order to obtain a specific relationship between rotation of the shaft 24d and variation of the resistance.

In all of the above described embodiments, the resistance elements have been disposed in parallel, fiat planes which are normal to the axis of rotation of shaft 24d, with the contact member moving in a flat, radial plane between the resistance elements. However, the present invention is not limited to such an arrangement and, as sown in Fig. 13, a potentiometer 20e may be provided, in accordance with the invention, wherein the resistance elements 2% and 30s are disposed in concentric, spaced apart, cylindrical surfaces of revolution, with the contact member, generally identified by the reference numeral 28a being movable within an annular space defined between the two resistance elements.

The casing of potentiometer 20a is, as before, formed of an insulating material, and includes an outer cylindrical wall 22:: and an inner cylindrical wall 21e defining an annular space 61 therebetween. An end wall 62 may be provided between the walls 21c and 22e at one end of the space 61, and a circular end wall 63 is secured to the opposite end of the outer cylindrical wall 222 and spaced from the adjacent end of inner wall Zle so that a radial space 64 is defined between end wall 63 and the adjacent end of cylindrical wall 211?. An actuating shaft 24a is journalled centrally in the end wall 63 and extends through the space 64 to carry a radially extending arm 26e which is movable angularly in space 64 as shaft 24e is rotated by a knob 256. At its radially outer end, arm 26:? carries a contact support rod 65 which extends through space 61 parallel to the axis of rotation of shaft 241;, and hence parallel to the concentric axes of cylindrical walls EL? and 222. In order to provide stability for the rod 65, the end of the latter remote from arm 26e may be slidably engaged as at 66, in a circular guide groove 67 formed in the front face of end wall 62.

In the embodiment of the invention shown in Fig. 13, the resistance elements 296 and 30e are helically disposed on the inner and outer surfaces of the walls 22e and 21e, respectively, within corresponding helical grooves 34e and 35a. The opposite ends of the helical grooves 342 and 35e are axially aligned so that, following travel of the contact member 28e along the resistance element 29:: in groove Me, the contact member can be shifted into engagement with the resistance element 30a in groove 35e. Thus, as shaft 24a is continuously rotated, contact member 28:: follows successive helical paths within space 61 which are respectively parallel to the resistance elements 2% and 302.

While the adjacent ends of the guide grooves 34c and 35e are not illustrated in Fig. 13, it is to be understood that such adjacent ends are inclined, in the same manner as the ends 36 of the grooves 34 and 35 in Fig. 4, as to effect shifting of the contact member from engagement with one of the resistance elements into engagement with the other of the resistance elements.

As seen in Fig. 14, the contact member 28a of the potentiometer 20e illustrated in Fig. 13 preferably includes a sleeve 68 slidable axially along the rod 65, and having a V-shaped member 69 which is pivotally mounted at its apex, as at 70, on the sleeve 68. The free ends of the legs of the V-shaped member 69 carry outwardly directed contacts 71 and 72 for engagement with the resistance elements 219:: and 30a within the guide grooves 34e and 356, respectively. When member 69 is angularly positioned with respect to sleeve 68, as shown in solid lines on Fig. 14, contact 72 engages against resistance element 302 within guide groove 35a, while angular displacement of member 69 to the broken line position of Fig. 14, moves contact 71 into engagement with the resistance element 292 within guide groove 342 and releases contact 72 from the related resistance element and guide groove. In order to yieldably hold member 69 in each of its positions described above, the member 69 is formed with a projection 73 between its legs which is disposable on one side or the other of a leaf spring member 74 so that the latter yieldably resists movement of the projection 73 from one side to the other of the leaf spring.

Since the resistance elements 29e and 3% are helically arranged within potentiometer 20c, it is apparent that each complete revolution of shaft 24c causes the contact member 28c to traverse an equal length of the resistance elements so that the variation of the resistance is a linear function of the rotational movement of knob c and shaft 24e.

While the resistance elements 29:: and 302 are both helically arranged in the potentiometer 2tle, and have the same number of turns, it is to be understood that the present invention is not limited to such an arrangement. For example, the resistance element a and its guide groove c may be helically arranged on the inner cylindrical wall 212, while the other resistance element 29:: and its guide groove 346 may constitute only a relatively short return path for the contact member from one end of the groove 35c to the other or initial end of that groove.

If the short return path has a relatively large pitch, rotation of shaft 24e may not be effective to produce movement of the contact member 282 along the return path.

In that case, a spring 75 may be provided on rod between a fixed abutment 76 and the sleeve 68 of the contact member to urge the latter axially in the direction toward the starting end of the helically arranged resistance element so that, when the contact member engages the resistance element and guide groove defining the short,

return path, spring will assist in causing the contact member to travel along that short return path.

In all of the foregoing structural embodiments of the invention, the contact member has been guided along the resistance element and, in those cases where applicable, the shifting of the contact member from one resistance element to the other resistance element has been effected, by suitably shaped guide grooves. However, as shown in Figs. 18 and 19, other structures may be provided for performing the above stated functions. In the arrangement of Figs. 18 and 19, the contact member 28f is guided along the resistance element 29 provided on wall 22 by a pair of spaced ridges 34f extending from the opposite wall 21] parallel to the path of the resistance element 29 and engageable with the end of the contact member 28f remote from the end of the latter which engages resistance element 29 Similarly, spaced ridges 35f extend from the wall 22 parallel to the resistance element 30f on wall 21f to guide contact member 28f during contact of the latter with resistance element 30 Preferably, as seen in Fig. 18, the adjacent ends of ridges 34 and 35 are inclined, as at 36 and the contact member 28] is provided with annular flanges 77 and 78, adjacent its opposite ends, for engagement with the edges of the ridges 341- and 35 respectively, so that, as the contact member reaches the end of one of the resistance elements, for example, the resistance element as in Fig. 18, flange 77 then rides upon the inclined portion 36 of ridges 34 while flange 78 simultaneously rides on the inclined portion of the ridges 35 thereby to shift the contact member from engagement with the terminal portion of resistance element 30 into engagement with the initial portion of resistance element 29 While the above described embodiments of the invention differ from each other in structural details, it is to be observed that all of these embodiments have in common the provision, in a potentiometer or the like, of resistance elements carried by two spaced apart walls, whereby a resistance capable of great variation, or of variation as a particular function of the movement of the actuating knob, may be obtained. Further, while various embodiments of the invention have been described in detail and illustrated in the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments, and that various changes and modifications may be eifected therein, by one skilled in the art, without departing from the scope or spirit of the invention as defined in the appended claims.

What I claim is:

l. A potentiometer or the like comprising two spaced apart, parallel walls of insulating material, resistance elements on the confronting faces of said walls with the ends of said resistance elements registering across the space between said walls', contact means movable along a closed path in said space, and guide means cooperating with said contact means and constraining the latter to successively engage said resistance elements during movement of said contact means along said closed path.

2. A potentiometer or the like according to claim 1; wherein said guide means includes a guide groove in each of said confronting faces of the walls parallel to the path to be followed by the contact means along the related resistance element.

3. A potentiometer or the like according to claim 2; wherein each of said resistance elements is disposed in the related guide groove.

4. A potentiometer or the like according to claim 1; wherein said guide means includes a pair of track defining ridges on each of said confronting faces of the walls, the track on each of said walls being parallel to the path to be followed by said contact means along the resistance element on the other of said walls, said contact means including means engageable between said track defining ridges.

5. A potentiometer or the like according to claim 1; wherein said contact means is movable in the direction extending laterally across said space, and said guide means includes portions corresponding to said registering ends of the resistance elements to shift said contact means in said direction from engagement with one resistance element into engagement with the other resistance element when said contact means reaches the end of said one element during movement along said path; and further comprising detent means for yieldably holding said contact means in the positions thereof where it is engageable with said one resistance element and with said other resistance element, respectively.

6. A potentiometer or the like comprising two spaced apart, parallel discs of insulating material, resistance elements on the confronting faces of said discs with the ends of said resistance elements registering across the space between said discs, contact means in said space, a central, rotatable shaft between said discs, support means mounting said contact means on said shaft and permitting movement of said contact means relative to said shaft in both the radial and axial directions, guide means cooperating with said contact means and constraining the latter to follow a path along said resistance elements, said guide id means being operative to shift said contact means axially from engagement with one of said elements to engagement with the other of said elements at said registering ends of the resistance elements.

7. A potentiometer or the like comprising two spaced apart, parallel discs of insulating material, guide grooves formed in the confronting faces of said discs with the ends of said guide grooves registering across the space between said discs, a resistance element in each of said grooves, said resistance elements being connected in series, at least one of said guide grooves and the related resistance element being spirally arranged, a contact memher, a rotatable shaft, means supporting said contact member on said shaft for rotation with the latter and permitting radial displacement of said contact member so that the latter is free to follow the paths of said guide grooves and axial displacement so that the contact member can be alternately engaged in said guide goooves in contact with the resistance elements in the latter, means at the ends of said guide grooves to effect axial displacement of said contact member from engagement with one of said grooves and the resistance element therein into engagement with the other of said grooves and the resistance element in the latter as said contact member reaches the end of said one groove.

8. A potentiometer or the like according to claim 7; wherein said contact member has a length substantially equal to the distance across said space from one of said confronting surfaces to the resistance element in the guide groove in the other of said confronting surfaces, and wherein said means for cifecting axial displacement of the contact member includes parallel inclined end portions at said registering ends of the guide grooves merging into said confronting surfaces of the discs.

9. A potentiometer or the like comprising two spaced apart, parallel discs of insulating material, oppositely directed spirals of resistance material on the confronting faces of said discs with the ends of said spirals registering across the space between said discs, contact means in said space, a rotatable support for said contact means, and means for guiding said contact means along the turns of said spirals during rotation of said support.

10. A potentiometer or the like according to claim 9; wherein said spirals of resistance material are electrically connected in series at one of the registered ends thereof, and said guiding means is operative to guide said contact means along the turns of said spirals in repeated succession; and further comprising terminals connected to said contact means and to one of said spirals of resistance material at the other end of the latter whereby rotation of said support varies the resistance between said terminals from a value of substantially zero to a value represented by the combined resistance of said spirals.

11. A potentiometer or the like according to claim 9; wherein said contact means includes two electrically connected contacts simultaneously engaging said spirals of resistance material at complementary locations on said spirals; and further comprising terminals respectively connected to the opposite ends of said spirals so that the resistance between said spirals varies as a linear function of the rotation of said support.

12. A potentiometer or the like comprising two spaced apart parallel walls of insulating material, resistance elements on the confronting faces of said walls with the ends of said elements being registered across the space between said walls, contact means movable through said space, a rotatable support for said contact means, means guiding said contact means during movement through said space to follow and engage said elements in succession, at least one of said elements including several turns, and indicating means including a pointer rotatable with said support and radially movable with respect to the latter, an indicating surface normal to the axis of rotation of said support and disposed in back of said pointer, said indicating surface having a spiral guide groove therein and a calibrated spiralled scale having a corresponding number of turns, means on said pointer engaging in said groove to radially displace said pointer during rotation of said support so that the pointer is in reading relationship to the portion of said scale corresponding to the position of said contact means along said elements, and a return groove connecting the inner and outer ends of said spiral guide groove to return said pointer to its original position during movement of said groove engaging means along said return groove.

13. A potentiometer or the like comprising two spaced apart parallel walls of insulating material, resistance elements on the confronting faces of said walls, means defining guide tracks on said confronting faces parallel to said resistance elements, contact means movable through the space between said walls, support means carrying said contact means for moving the latter along a closed path, and rollers on said contact means for low-friction cngage ment with said guide tracks so that said contact means follows said resistance elements during movement of said contact means along said closed path.

14. A potentiometer or the like comprising two spaced apart, parallel walls of insulating material, resistance elements on the confronting faces of said walls, means defining guide tracks on said confronting faces at locations spaced from the related resistance elements, contact means movable through the space between said walls for engagement with the resistance elements, and means joined to said contact means and engageable with said guide tracks so that the latter control the paths of said contact means during engagement of the latter with said resistance elements.

15. A potentiometer or the like comprising two spaced apart, parallel Walls of insulating material, resistance elements on the confronting faces of said walls, one of said resistance elements being arranged as a spiral of several turns and the other of said elements defining a short return path between the opposite ends of said one element, contact means in the space between said walls, rotatable support means carrying said contact means, and guide means operative to guide said contact means successively along said one element and said other element during the continuous rotation of said support means in one direction.

16. A potentiometer or the like comprising an outer cylindrical wall and an inner, concentric cylindrical wall spaced from said outer wall, resistance elements on the confronting surfaces of said walls and having their opposite ends registered in the axial direction, at least one of said resistance elements being in the form of a helix of several turns, contact means in the annular space between said walls, means supporting said contact means for rotational and axial movement through said space, and guide means operative to constrain said contact means to follow and engage said resistance elements successively during rotational movement of said contact means through said space.

17. A potentiometer or the like according to claim 16; wherein said guide means includes grooves in said confronting surfaces of said walls and receiving said resistance elements, said supporting means includes a rod extending parallel to the axes of said cylindrical walls and movable along a circular path in said space, and said contact means includes a sleeve slidable axially on said rod, a member rockable on said sleeve and having two oppositely directed contacts thereon for alternate engagement with the resistance elements in the guide grooves in the inner and outer walls, respectively, and means for yieldably holding said rockable member in each of two positions relative to said sleeve wherein one of said contacts engages the resistance element on the inner wall and wherein the other of said contacts engages the element on the outer wall, respectively.

18. A potentiometer or the like according to claim 16; wherein only one of said resistance elements is in the form of a helix, the other of said resistance elements and the related guide means defining a relatively short return path between the ends of the helical element, and said supporting means includes a rod in said space extending parallel to the axes of the cylindrical walls and following a circular path in said space, said contact means being axially slidable on said rod; and further comprising spring means acting on said contact means to urge the latter axially along said rod during engagement of said contact means with said other resistance element.

References fiited in the file of this patent UNITED STATES PATENTS 2,350,607 Gonsett et al June 6, 1944 2,412,062 Reisberg et a1 Dec. 3, 1946 2,454,986 Beckman Nov. 30, 1948 

